Tape storage device

ABSTRACT

A method, and apparatus configured to perform such method, according to various embodiments, includes writing data stored in a buffer onto a recording medium using a write head in a first round of writing. An interval marker is written on the recording medium in the first round of writing when the buffer is empty. Next data is written onto the recording medium after the interval marker in the first round of writing. Data is written in an area of the interval marker in a second round of writing performed subsequent to the first round.

This application is a continuation of U.S. patent application Ser. No.13/734,853 tiled Jan. 4, 2013, which is herein incorporated byreference. This application claims priority to Japanese PatentApplication No. 2012-000308, filed Jan. 5, 2012, which is hereinincorporated by reference.

BACKGROUND

The present invention relates to a tape storage device, and morespecifically, it relates to data writing control for a tape storagedevice.

Existing tape storage devices are based on the premise that, inrecording data from a host on tape, items of data are sequentiallyrecorded in a data track. If the amount of data input from a host perunit time is smaller than the amount of data written on tape, the tapetransportation is stopped and the tape is rewound (back hitched), oralternatively, the tape transportation speed is reduced and items ofdata are sequentially recorded in a data track densely.

BRIEF SUMMARY

An apparatus according to one embodiment includes a controllerconfigured to write, by the controller, data stored in a buffer to arecording medium in a first round of writing. An interval marker iswritten in the first round of writing when the buffer is empty. Nextdata is written on the recording medium after the interval marker in thefirst round of writing. Data is written in an area of the intervalmarker on the recording medium in a second round of writing performedsubsequent to the first round.

A method according to one embodiment includes writing data stored in abuffer onto a recording medium using a write head in a first round ofwriting; writing an interval marker on the recording medium in the firstround of writing when the buffer is empty; writing next data onto therecording medium after the interval marker in he first round of writing;and writing data in an area of the interval marker in a second round ofw performed subsequent to the first round.

A computer program product for writing data onto a recording mediumincludes a computer readable storage medium having program code embodiedtherewith. The program code is readable/executable by a controller towrite, by the controller, data stored in a buffer onto a recordingmedium in a first round of writing using a head; write, by thecontroller, an interval marker on the recording medium at a locationafter the data; write, by the controller, next data on the recordingmedium after the interval marker in the first round; and write, by thecontroller, data stored in the buffer in an area of the interval markerin a second round performed subsequent to the first round.

Any of these embodiments may be implemented in a magnetic data storagesystem such as a tape drive system, which may include a magnetic head, adrive mechanism for passing a magnetic medium (e.g., recording tape)over the magnetic head, and a controller electrically coupled to themagnetic head.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 depicts a schematic diagram of a of a file system that uses atape storage device according to one embodiment.

FIG. 2 depicts a schematic diagram of a tape storage device according toone embodiment.

FIGS. 3A-3B depict schematic diagrams of a read-and-write (R/W) head andits peripheral circuit according various embodiments.

FIGS. 4A-4D depict schematic diagrams of states of writing in a portionof a tape according to various embodiments.

FIGS. 5A-5B depict schematic diagrams of positional relationshipsbetween a R/W head and a tape according to one embodiment.

FIG. 6 depicts a flowchart of a method according to one embodiment.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” an and “the” include pluralreferents unless otherwise specified.

The following description discloses several preferred embodiments oftape storage devices, as well as operation and/or component partsthereof.

In one general embodiment, a device includes a controller, such as atape storage chip, board, and/or circuit, configured to perform controlfor: (i) writing the data stored in the buffer, subsequently writing aninterval marker without interruption after the buffer is empty of thestored data, and writing next data subsequently to the interval markerwhen the next data is stored in the buffer in a first roundcorresponding to a first-time write in a single track in the tape, (ii)writing data stored in the buffer in an area of the interval marker in asecond round corresponding to a second-time write in the single track,and (iii) writing data stored in the buffer in the area in which no datais written of the interval marker in each of third and subsequent roundscorresponding to third- and subsequent-time writes in the single track.

In another general embodiment, a method includes writing data stored ina buffer onto a tape; writing an interval marker on the tape after thedata stored in the buffer is written onto the tape; writing next datasubsequent to the interval marker when the next data is stored in thebuffer in a first round corresponding to a first-time write in a singletrack in the tape; writing data stored in the buffer in an area of theinterval marker in a second round corresponding to a second-time writein the single track; and writing data stored in the buffer in an area ofthe interval marker in which no data is written in each of third andsubsequent rounds corresponding to third- and subsequent-time writes inthe single track.

Back hitching or variable-speed tape transportation to sequentiallyrecord items of data on a data track typically needs a mechanism forminutely controlling a reel motor, e.g. a mechanism for controlling atape transportation speed in several steps or steplessly. Accordingly,various embodiments of the present invention provide data writingcontrol by which complex control of tape transportation, movement of theposition of a read-and-write (R/W) head, or other intricate control inthe above-described technique may be eliminated or reduced in datawriting in a tape storage device.

Several preferred embodiments of the present invention provide a tapestorage device including a read-and-write (R/W) head capable of writingdata after reading data, a buffer configured to store data to be writtenon tape and data read from the tape by the R/W head, a motor driverconfigured to control a motor for transporting the tape, and acontroller configured to control the R/W head and the motor driver.Preferably, after instructing the motor driver to transport the tape ata constant speed, the controller in the tape storage device may performcontrol for (i) writing the data stored in the buffer, subsequentlywriting an interval marker without interruption after the buffer isempty of the stored data, and writing next data subsequently to theinterval marker when the next data is stored in the buffer in a firstround corresponding to a first-time write in a single track in the tape,(ii) writing data stored in the buffer in an area of the interval markerin a second round corresponding to a second-time write in the singletrack, and (iii) writing data stored in the buffer in the area in whichno data is written of the interval marker in each of third andsubsequent rounds corresponding to third- and subsequent-time writes inthe single track.

In some embodiments of the present invention, because data may bewritten while the tape is transported at a constant speed, complexcontrol of tape transportation, such as back hitching and variable-speedtape transportation, may be avoided. In addition, production of aninterval marker in the same track in the tape and use of the intervalmarker (a plurality of writes in the interval marker) may prevent adecrease in the amount of stored data (density) per one track.

According to one embodiment, a controller may perform control forwriting the data stored in the buffer in the area of the interval markerwhen a data fill ratio (e.g. the amount of written data in onetrack/capacity of one track) for the single track does not exceed apredetermined value. Additionally, an overflow in writing data in thesingle track may be avoided, and, substantially the same or similaramount of writing data may be ensured in each track.

According to another embodiment, the controller may perform control forwriting the data stored in the buffer in a next new track when the datafill ratio for the single track exceeds the predetermined value.Furthermore, complex control for movement of the position of the headmay be avoided.

According to yet another embodiment, the controller may update the datafill ratio for the single track in an end or a beginning of the singletrack. In some approaches, a track in which data is to be written may beappropriately selected while, at the same time or near the same time,the latest data fill ratio for the track may be grasped before a writein each round.

According to a further embodiment, the controller may perform controlfor retaining the data fill ratio for the single track in either one orboth of a housekeeping area in the single track or another track in thetape and a cartridge memory of a cartridge holding the tape. In someapproaches, storing the data fill ratio for the single track in the tapeor the cartridge itself may enable writing control using this data fillratio in different (other) tape storage devices.

According to various embodiments, the data may be written in the area ofthe interval marker by the R/W head after a predetermined time since abeginning of the interval marker in the area of the interval marker isread by the R/W head. In addition, data may be automatically written(overwritten) in the area of the interval marker simply by detection(reading) of this interval marker.

According to some approaches, when the predetermined time is T, T may beexpressed by the Wowing equation:

T=L/V(s)

where L denotes a distance (m) between a write (W) head and a read (R)head in the RAY head and V denotes a transportation speed (m/s) of thetape. The time (position) to start writing data may also beappropriately and precisely set from detection (reading) of the intervalmarker.

Referring now to FIG. 1, a schematic diagram of a file system that mayuse a tape storage device is shown according to one illustrativeembodiment. A file system 100 includes a tape storage device 10, a host(e.g. a server) 30, and user devices 32 and 34. Such user devices mayinclude, but are not limited to personal computers (PCs), terminals,desktop computers, handheld computers, etc or any other type of logic.The tape storage device 10, host (server) 30, and user devices 32 and 34are connected to each other over a network 36 such that they cancommunicate with each other. FIG. 1 depicts one tape storage device 10and one host (server) 30 for illustrative purposes only. Obviously, thefile system 100 may include two or more tape storage devices 10 andhosts (servers) 30. The tape storage device according to the presentinvention is not limited to being used as part of the file system 100and may also be used in any form where it can be connected to the host(server) 30 and user devices 32 and 34.

FIG. 2 illustrates a schematic diagram of a tape storage device 10according to another illustrative embodiment. The tape storage device 10includes a host interface (hereinafter referred to as “host I/F”) 11, abuffer 12, a channel 13, a read-and-write (R/W) head 14, and a motor 15.The tape storage device 10 further includes a controller 16, a headposition control system 17, and a motor driver 18. A tape cartridge 20may be loaded in the tape storage device 10 by being inserted therein asalso shown in FIG. 2, The tape cartridge 20 includes tape 23 wound onreels 21 and 22. Together with rotation of the reels 21 and 22, the tape23 longitudinally moves in the direction from the reel 21 to reel 22 orthe direction from the reel 22 to the reel 21. In some approaches, tape23 may be magnetic tape or other suitable tape medium as understood byone having skill in the art upon reading the present disclosure.

As shown in FIG. 2, the tape cartridge 20 also includes a cartridgememory (CM) 24, The CM 24 records information indicating how data iswritten on the tape 23. The data may be accessed at high speed by, forexample, consulting an index of the data written on the tape 23, statusof use of the tape 23, and the like, by the use of an RE interface in anoncontact manner. The CM 24 may also record a data fill ratio (e.g. theamount of written data/capacity of one track) for each track in thetape. The data fill ratio is used in data writing control for each trackdescribed below. The interface used in accessing the CM 24, such as theRE interface, is represented as a cartridge memory interface(hereinafter referred to as “CM I/F”) 19 in FIG. 2.

The host I/F 11 communicates with the host (server) 30, the user device32, and other apparatuses. For example, the host I/F 11 receives, fromthe OS in the host 30, a command to write data on the tape 23, a commandto move the tape 23 to a target position, and a command to read datafrom the tape 23. In the exemplary schematic diagram illustrated in FIG.1 described above, data in the tape storage device may be directlyreferred to from the OS in a desktop computer, and the data can beexecuted by double clicking and can be copied by drag-and-drop, as inthe case of handling a file in a hard disk.

With the continued reference to FIG. 2, the buffer 12 may be a memorythat stores data to be written on the tape 23 and data read from thetape 23. For example, the buffer 12 may be a dynamic random accessmemory (DRAM). The buffer 12 may include a plurality of buffer segments,each of which stores a data set that is a unit for reading and writingdata from and on the tape 23. The channel 13 may be a communication pathfor use in transmitting data to be written on the tape 23 to the R/Whead 14 and in receiving data read from the tape 23 from the R/W head14.

The R/W head 14 writes information on the tape 23 and reads informationfrom the tape 23 while the tape 23 moves in the longitudinal direction.Although FIG. 2 depicts only one RAY head 14, in some embodiments theremay be two or more R/W heads 14, one for the forward direction ofmovement of the tape 23 and the other for the backward directionthereof. The details of the R/W head 14 are described below.

As shown in FIG. 2, the motor 15 rotates the reels 21 and 22. The motor15 is depicted as a single rectangle in FIG. 2; however, in preferredembodiments, two motors 15, one for each of the reels 21 and 22, may beprovided.

The controller 16 exercises control over the tape storage device 19. Forexample, the controller 16 may control writing data on the tape 23 andreading data from the tape 23 in accordance with a command received bythe host 11. The controller 16 may also control the head positioncontrol system 17 and the motor driver 18. The data writing controlperformed by the controller 16 is described below.

As also shown in FIG. 2, the head position control system 17 may be asystem that keeps track of a desired lap. The lap used herein mayindicate a group of a plurality of tracks on the tape 23. If it becomenecessary to switch a lap, it may also become necessary to electricallyswitch the head 14. This kind of switching control may be performed bythe head position control system 17.

The motor driver 18 drives the motor 15. As previously described, if twomotors 15 are used, two motor drivers 18 may be provided. The CM PP 19may be achieved by an RF reader-writer, for example, and writesinformation in the CM 24 and reads information from the CM 24.

Referring now to FIGS. 3A-3B, schematic diagrams 300, 301 of a R/W headand its peripheral circuits are shown according to illustrativeembodiments. FIG. 3A illustrates an RV head 144 used when the tape 23 istransported in the forward direction (direction indicated by the arrowF) and FIG. 3B illustrates an RV head 14B used when the tape 23 istransported in the backward direction (direction indicated by the arrowB). Only the head section is illustrated in FIG. 3B, and the peripheralcircuit is omitted in FIG. 3B because it is the same as in FIG. 3A. Eachof the R/W heads 14A and 14B includes at least one read (R) head 141 andone write (W) head 143. The read (R) head 141 is located to the left ofthe write (W) head 143 in FIG. 3A, However, as shown in FIG. 3B, theread (R) head 141 is located to the right of the write (W) head 143. Thereason why the arrangements in FIGS. 34 and 3B are different is thatdata is written after the read (R) head, which is positioned in advanceof the write (W) head in the respective tape travel directions shown,detects (reads) the area of an interval marker, as described in moredetail below, in a track of the tape in the forward transportationdirection (direction indicated by the arrow F in FIG. 3A) and thebackward transportation direction (direction indicated by the arrow B inFIG. 3B). The read (R) head 141 is spaced away from the write (W) head143 by a predetermined distance L. If the tape storage device includes amechanism for reversing the direction of the R/W head in synchronizationwith a reversal of the direction of transportation of the tape F->B orB->F), the R/W head may be either one of the R/W heads 14A and 14B.

An interval marker detector 145 illustrated in FIG. 3A detects aninterval marker from a signal (information) read by the read head 141.The interval marker used herein may be information that indicatesvacancy and may be different from a user data set. One example of theinterval marker may be a data set separator. The interval marker mayalso include a predetermined pattern in some approaches. The intervalmarker detector 145 may detect the interval marker by reading thepredetermined pattern included in the interval marker.

In response to a detection signal from the interval marker detector 145,a delay processing circuit 146 may send a delay signal subjected to adelay of a predetermined time to a gate circuit 147. The predeterminedtime may be set in the way described below. For example, when thepredetermined time is T(s), T may be set in various approaches asfollows:

T=L/V(s)   (1)

where L denotes the distance (m) between the write (W) head 143 and theread (R) head 141 in the R/W head and V denotes the transportation speed(m/s) of the tape.

The predetermined time may be set in this way because the data writingcontrol in the present invention may be performed based on the premisethat the tape is transported at a constant speed, as described below.Thus, the time (position) to start writing data in the area of aninterval marker may be appropriately and precisely set from detection(reading) of this interval marker.

In response to the delay signal from the delay processing circuit 146,the gate circuit 147 may perform control for sending data stored in thebuffer 12 to the write (W) head 143 in writes in a single track in thetape in the second and subsequent rounds, according to some approaches.Write data in the second and subsequent rounds may be sent to the write(W) head 143 through the channel 13 in more approaches.

According to various embodiments, the writing control performed by thecontroller 16 (shown, e.g. in FIG. 2) may be described with reference toFIGS. 4A-4D and FIG. 5. For instance, FIGS. 4A-4D illustrate exemplaryschematic diagrams 400 of states of writing in the forward direction(direction indicated by the arrow F) and in the backward direction(direction indicated by the arrow B) of the tape. in writing in theforward (F) direction in FIGS. 4A-4D, the R/W head 144 illustrated inFIG. 3A described above may be used; in writing in the backward (B)direction, the R/W head 14B illustrated in FIG. 3B may be used. In FIGS.4A-4D, the tape 23 may be transported at a constant speed in both theforward direction and backward direction by control on the motor driver18 by the controller 16. Additionally, FIGS. 5A-58 illustrate schematicdiagrams 500, 501 of positional relationships between the R/W head andthe tape according to the present invention.

Referring first to FIGS. 4A to 4D in sequence, FIG. 4A illustrates anexample of writing in a first track in the first round in the forwarddirection; FIG. 4B illustrates an example of writing in a second trackadjacent to the first track in the first round in the backwarddirection; FIG. 4C illustrates an example of writing in the first trackin the second round in the forward direction; and FIG. 4D illustrates anexample of writing in the second track in the second round in thebackward direction. In some approaches, writes on the tape 23 in thesame direction may be counted as the first round, second round, . . . insequence. Accordingly, FIG. 4A may correspond to writing in the firstround in the forward direction; FIG. 4C may correspond to writing in thesecond round in the forward direction; FIG. 4B may correspond to writingin the first round in the backward direction; and FIG. 4D) maycorrespond g in the second round in the backward direction.

As shown in FIG. 4A according to one embodiment, after the buffer 12(FIG. 2) is empty of data after first-round data 1 from the buffer 12 iswritten, an interval marker 231 may be subsequently written in the firsttrack without interruption. When data from the host 30 is stored in thebuffer 1 this data may be written as first-round data 2 after theinterval marker 231. After the buffer 12 is empty of data again, aninterval marker 232 may subsequently be written without interruption.When data from the host 30 is stored in the buffer 12, this data may bewritten as first-round data 3 after the interval marker 232. Such awriting operation may be repeated from the beginning (BOT) to the end(EOT) of the tape 23.

When the end of the first track in the first round (EOT of the tape) isreached in FIG. 4A, the controller 16 (FIG. 2) may temporarily stop thetransportation of the tape in some approaches. The controller 16 mayperform control for calculating the data fill ratio (e.g. the amount ofwritten data/capacity of one track) for the first track and retainingthe data fill ratio in either one or both of a housekeeping area (notillustrate that track or another track and the CM 24 (FIG. 2). Thecontroller 16 may also determine whether the data fill ratio for thefirst track does not exceed a predetermined value. Examples of thepredetermined value may include about 50%, about 80%, about 90%, etc.The predetermined value may be set at an appropriate value as areference value for determining whether further data is to be written inthat track.

In various approaches, the controller 16 (FIG. 2) may control the headposition control system 17 so as to start writing data in the adjacentsecond track in the first round in transportation in the backwarddirection from the end (EOT) to the beginning (BOT) of the tape 23 bythe R/W head 14, as illustrated in FIG. 4B. With regard to writing inthe second track (illustrated in FIG. 411) as a continuation of thewriting in the first track (illustrated in FIG. 4A), after the buffer 12is empty of data after first-round data 4 from the buffer 12 is written,an interval marker 233 may be subsequently written in the second trackwithout interruption. Further, when data from the host 30 is stored inthe buffer 12, this data may be written as first-round data 5 after theinterval marker 233. After the buffer 12 is empty of data again, aninterval marker 234 may be subsequently written without interruption.Such a writing operation may be repeated from the end (EOT) to thebeginning (BOP) of the tape 23.

In more approaches, when the end of the second track in the first round(BOT of the tape) is reached in FIG. 48, the controller 16 (FIG. 2) maytemporarily stop the transportation of the tape, calculate the data fillratio for the second track, retain the data fill ratio, and determinewhether the data fill ratio does not exceed a predetermined value bycomparing it against a predetermined value, as in the case of FIG. 4Adiscussed above.

When the data fill ratio for the first track does not exceed thepredetermined value, the controller 16 may write data in the first trackin the second round, as illustrated. in HG. 4C according to variousapproaches. When the data fill ratio for the first track exceeds thepredetermined value, further writing data in the first track may becanceled, and writing may move to another new track. For instance, FIG.4C illustrates an example of writing in which second-round data 6 (235)and second-round data 7 (236) are sequentially written in the areas 231and 232 of the interval markers, respectively. In this writing, aspreviously described with reference to FIGS. 3A-3B, while intervalmarkers may be detected by the interval marker detector 145, items ofdata may be sequentially written after a predetermined time since eachof the detections. Consequently some embodiments of the presentinvention feature writing data while determining the data till ratio foreach track and in addition while detecting the area of an intervalmarker in each track.

Further, according to some approaches, when the end of the first trackin the second round (EOT of the tape) is reached in FIG. 4C, thecontroller 16 may temporarily stop the transportation of the tape,calculate the data fill ratio for the first track, retain (update) thedata fill ratio, and determine whether the data fill ratio does notexceed a predetermined value by comparing it against the predeterminedvalue, as in the case of FIG. 4A.

When the data fill ratio for the second track does not exceed thepredetermined value, the controller 16 may write data in the secondtrack in the second round, as illustrated in FIG. 4D according someapproaches. When the data fill ratio for the second track exceeds thepredetermined value, further writing data in the second track may becanceled, and writing may move to another new track in other approaches.FIG. 4D illustrates an example of writing in which second-round data 8(237) and second-round data 9 (238) may be sequentially written in thearea 233 of the interval marker.

In additional approaches, when the end of the second track iii thesecond round (BOT of the tape) is reached in FIG. 40, the controller 16may temporarily stop the transportation of the tape, calculate the datafill ratio for the second track, retain (update) the data fill ratio,and determine whether the data fill ratio does not exceed apredetermined value by comparing it against a predetermined value, as inthe case of FIG. 4A. Data may be written in the first and second tracksin the third and subsequent rounds using substantially the same orsimilar procedure as in the case of FIG. 4C or 4D. Such writing controlby the controller 16 may be performed on each track successively insubstantially the same way.

Referring now to FIG. 5A, a schematic diagram 500 of a positionalrelationship between the R/W head 14A and the tape 23 in detecting aninterval marker in transportation in the forward direction (F direction)is shown according to another illustrative embodiment. The intervalmarker may first be read by the read (R) head of the R/W head 14A inthis transportation in the forward direction, as illustrated. Data maybe written (overwritten) by the write (W) head in the read intervalmarker (area), as illustrated in the example of FIG. 4C. In a locationwhere no interval marker is detected by the interval marker detector145, in other words, in a location where no interval marker is read bythe read (R) head, writing data by the write (W) head may he stopped insome approaches. The point A is the end point of reading the intervalmarker in FIG. 5A, and writing data may be stopped in response to thedetection of this end point (point A).

Referring now to FIG. 5B, a schematic diagram 501 of a positionalrelationship between the R/W head 14B and the tape 23 in detecting aninterval marker in transportation in the backward direction (Bdirection) is shown according to yet another embodiment. The intervalmarker may be read by the read (R) head of the R/W head 14B in thistransportation in the backward direction, as illustrated. Data may bewritten (overwritten) by the write (W) head in the read interval marker(area), as illustrated in the example of FIG. 4D. In a location where nointerval marker is read by the read (R) head, writing data by the write(W) head may stopped in some approaches, as in the case of FIG. 5A.

Now referring to FIG. 6, a method 600 is shown in accordance with oneembodiment. As an option, the present method 600 may be implemented inconjunction with features from other embodiments listed herein, such asthose described with reference to the other FIGS. Of course, however,such method 600 and others presented herein may be used in variousapplications and/or permutations, which may or not be specificallydescribed in the illustrative embodiments listed herein. Moreover, moreor less operations than those shown in FIG. 6 may be included in method600, according to various embodiments.

As shown in FIG. 6 according to one approach, the method 600 includeswriting data stored iii a buffer on a tape) and writing an intervalmarker on the tape after the data stored in the buffer is written on thetape. See operations 602 and 604, respectively. The method 600 alsoincludes writing next data subsequent to the interval marker when thenext data is stored in the buffer in a first round corresponding to afirst-time write in a single track in the tape. See operation 606.

Further, in operation 608, data stored in the buffer is written in anarea of the interval marker in a second round corresponding to asecond-time write in the single track. In one embodiment, the datastored in the buffer is written in the area of the interval marker bythe R/W head after a predetermined time since a beginning of theinterval marker in the area of the interval marker is read by the R/Whead. As used herein, the predetermined time (T) may be expressed by thefollowing equation:

T=L/V(s)

where L denotes a distance (m) between a write (W) head and a read Rhead in the R/W head and V denotes a transportation speed (m/s) of thetape.

Additionally, data stored in the buffer is written in an area of theinterval marker in which no data is written, in each of third aridsubsequent rounds corresponding to third- and subsequent-time writes inthe single track. See operation 610.

According to one embodiment, the method 600 may further includedetermining a data fill ratio for the single track, wherein the datatill ratio refers to an amount of written data on a single track dividedby a capacity of the single track. In some approaches, the data fillratio for the single track may be updated in an end of the single trackor a beginning of the single track. In other approaches, the data fillratio for the single track may be retained in at least one of ahousekeeping area in the single track or another track in the tape and acartridge memory of a cartridge holding the tape.

According to another embodiment, the data stored in the buffer in thearea of the interval marker may be written when the data fill ratio forthe single track does not exceed the predetermined value. According toyet another embodiment, the data stored in the buffer may be written inanother track when the data fill ratio for the single track exceeds thepredetermined value.

Numerous embodiments of the present invention have been described withreference to the drawings. It should be understood, however, that thepresent invention is not limited to the above-described embodiments. Forinstance, the present invention may be used in various applicationsand/or permutations, which may or not be specifically described in theillustrative embodiments listed herein. Moreover, any of the featurespresented herein may be combined in any combination to create variousembodiments, any of which fall within the scope of the presentinvention.

It will be clear that the various features of the foregoing systemsand/or methodologies may be combined in an any way, creating a pluralityof combinations from the descriptions presented above.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as “logic,” a “circuit,” “module,” or“system.” Furthermore, aspects of the present invention may take theform of a computer program product embodied in one or more computerreadable medium(s) having computer readable program code embodiedthereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a non-transitory computer readable storage medium. A computerreadable storage medium may be, for example, but not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, or device, or any suitable combinationof the foregoing. More specific examples (a non-exhaustive list) of thenon-transitory computer readable storage medium include the following: aportable computer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a portable compact disc read-only memory (e.g.,CD-ROM), a Blu-ray disc read-only memory (BD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a non-transitory computerreadable storage medium may be any tangible medium that is capable ofcontaining, or storing a program or application for use by or inconnection with an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a non-transitory computer readable storage medium and that cancommunicate, propagate, or transport a program for use by or inconnection with an instruction execution system, apparatus, or device,such as an electrical connection having one or more wires, an opticalfibre, etc.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fibre cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection ay be made to an externalcomputer, for example through the Internet using an Internet ServiceProvider (ISP).

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may a so be stored a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart(s) and/orblock diagram block or blocks.

It will be further appreciated that embodiments of the present inventionmay be provided in the form of a service deployed on behalf of acustomer.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of an embodiment of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. An apparatus comprising: a controller configuredto: write, by the controller, data stored in a buffer to a recordingmedium in a first round of writing; write, by the controller, aninterval marker in the first round of writing when the buffer is empty;write, by the controller, next data on the recording medium after theinterval marker in the first round of writing; and write, by thecontroller, data in an area of the interval marker on the recordingmedium in a second round of writing performed subsequent to the firstround.
 2. The apparatus according to claim 1, wherein the controller isconfigured to write data in an area of the interval marker in which nodata is written in each of third and subsequent rounds corresponding tothird- and subsequent-time writes.
 3. The apparatus according to claim1, wherein the controller is configured to write data in the area of theinterval marker in the second round when a data fill ratio for a singletrack written in the first round does not exceed a predetermined value,wherein the data till ratio refers to an amount of written data on thesingle track divided capacity of the single track.
 4. The apparatusaccording to claim 3, wherein the controller is configured to write thedata stored in the buffer in another track when the data fill ratio forthe single track exceeds the predetermined value.
 5. The apparatusaccording to claim 3, wherein the controller is configured to update thedata fill ratio for the single track in an end or a beginning of thesingle track.
 6. The apparatus according to claim 5, wherein thecontroller is configured to store the data fill ratio for the singletrack in at least one of the recording medium and a memory.
 7. Theapparatus according to claim 1, wherein the data is written in the areaof the interval marker by a head after a predetermined time has elapsedfrom when a beginning of the interval marker in the area of the intervalmarker is read by the head.
 8. The apparatus according to claim 7,wherein when the predetermined time (T) is expressed by the followingequation:T=L/V(s) where denotes a distance between a write portion and a readportion in the head and V denotes a transportation speed of therecording medium.
 9. The apparatus according to claim 1, furthercomprising: a head; a buffer configured to store data to be written onthe recording medium and data read from the recording medium by themagnetic head; and a motor driver configured to control a motor fortransporting the recording medium.
 10. A method, comprising: writingdata stored in a buffer onto a recording medium using a write head in afirst round of writing; writing an interval marker on the recordingmedium in the first round of writing when the buffer is empty; writingnext data onto the recording medium after the interval marker in thefirst round of writing; and writing data in an area of the intervalmarker in a second round of writing performed subsequent to the firstround.
 11. The method of claim 10, comprising writing data in an area ofthe interval marker in which no data is written in each of third andsubsequent rounds corresponding to third- and subsequent-time writes.12. The method of claim 11, wherein the next data is written in the areaof the interval marker in the second round by the head after apredetermined time has elapsed from when a beginning of the intervalmarker in the area of the interval marker is read.
 13. The method asrecited in claim 10, comprising determining a data fill ratio for asingle track written in the first round, wherein the data fill ratiorefers to an amount of written data on the single track divided by acapacity of the single track.
 14. The method as recited in claim 13,further comprising updating the data fill ratio for the single track inan end of the single track or a beginning of the single track.
 15. Themethod as recited in claim 13, comprising retaining the data fill ratiofor the single track in at least one of the recording medium and amemory.
 16. The method as recited in claim 13, further comprisingcomparing the data fill ratio to a predetermined value, wherein the datastored in the buffer is written in the area of the interval marker whenthe data fill ratio for the single track does not exceed thepredetermined value.
 17. The method as recited in claim 16, wherein thedata stored in the buffer is written in another track when the data fillratio for the single track exceeds the predetermined value.
 18. Acomputer program product for writing data onto a recording medium, thecomputer program product comprising a computer readable storage mediumhaving program code embodied therewith, the program codereadable/executable by a controller to: write, by the controller, datastored in a buffer onto a recording medium in a first round of writingusing a head; write, by the controller, an interval marker on therecording medium at a location after the data; write, by the controller,next data on the recording medium after the interval marker marker inthe first round; and write, by the controller, data stored in the bufferin an area of the interval marker in a second round performed subsequentto the first round.
 19. The computer program product of claim 18,wherein the data stored in the buffer is written in the area of theinterval marker by the head after a predetermined time has elapsed fromwhen a beginning of the interval marker in the area of the intervalmarker is read by the head.
 20. The computer program product of claim18, comprising program code readable/executable by the controller towrite, by the controller, data in an area of the interval marker inwhich no data is written in each of third and subsequent roundscorresponding to third- and subsequent-time writes.